# Questions tagged [motors]

Questions regarding motors. All types of motors, their gearboxes, how to drive an electrical motor etc.

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### Will AC Motor Maintain Speed of Descending Object

Suppose we have an AC motor which needs to lower an object at a set speed. We use a PID loop to determine and correct positional errors. Presumably the PID loop will keep the current low as most of ...
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1 vote
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### Actuator recommendation for oscillating motion of a 6 kg object

I have a general question without many specific parameters, but I hope someone will be able to point me in the right direction - at least what actuator best serves my purpose. I am working on a ...
175 views

### How do DC motor parameters scale with motor size?

Consider the following DC motor parameters: Rotor resistance, $R\ [\Omega]$ Motor constant, $k_t\ [\mathrm{V/rpm}]$ Inertia, $I\ [\mathrm{kg\cdot m^2]}$ How do they scale with motor size? Do $R$ and ...
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### What determines the maximum torque of a DC motor?

What determines the maximum torque of a DC motor? How is this related to the equations $$E=k\omega$$ $$T=kI$$ where $E$ is electromagnetic force / voltage (V) $\omega$ is rotational speed (rad/s) \$...
• 540
146 views

### High RPM - Stepper vs Brushless Motor

I need to spin a threaded rod to raise a picture on a frame. The weight of the picture + the parts that it hangs on will be around 6 pounds. Two motors are going to be used to lift it via threaded ...
• 143
1 vote
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### Motor for inverted rotary pendulum

I'm building a rotary inverted pendulum to demonstrate reinforcement learning principles, however I have little experience with mechatronics. I will be building something similar to this. However ...
81 views

### How do I calculate the best mass for the highest linear speed?

I have a motor whose specifications say that its torque is 190g*cm. If I have the formula for the mass of the wheel vs radius, is there any way I can find the radius to get the best linear speed? The ...
2k views

### How to couple a motor to a screw drive?

I have a simple linear translation stage that is driven by a screw, and I would like to attach a stepper motor to the screw drive. The axis of the screw and the axis of the motor are approximately ...
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### Pneumatic Actuators - System Reversibility. Is it possible to use an actuator to store energy?

I'm very much new to pneumatics and I was wondering if there was such a thing as a reversible pneumatic actuator? I'm designing a system that has to be lightweight, pneumatic and use a mechanical ...
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### How are small refrigerator compressors started?

Small refrigerator compressors in the US generally all have exactly the same design and I am trying to understand their starting mechanism better. How exactly does it work? What I generally ...
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1 vote
1k views

### VFD/rheostat for motor speed control

I have a 3 phase motor and 3 phase power supply (400V, 50Hz) Currently this motor produces 1.5hp in torque and ~1750rpm. I need it to produce less. My question is: Is the best way to go about this, ...
• 11
142 views

### Which is more durable in sandy desert conditions: electric motors or hydraulic pistons?

If we have a tracking system placed in a tough desert environment with occasional sandstorms and temperatures that go as high as 50C, which actuator would be better: a hydraulic piston or an electric ...
1 vote
425 views

### Gearing for Multiple Forward / Reverse on Single Drive Shaft

This model illustrates my question: Red is a motor Green is the drive shaft Orange are nylon straps Blue are spools for the straps I want to be able to drive multiple spools in multiple directions ...
3k views

### What is the use of gears in a device with a fixed gear ratio?

From my understanding, there are two uses of a gearing system: to change the speed of output rotation (trading it with torque), and to change the axis of rotation. Now, in a car, for example, it is ...
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### How can I apply a load to an electric motor to simulate realistic conditions for an experiment?

I am trying to perform some experiments with a motor and I want to run it under realistic conditions (or at least not unloaded). Is there an easy way to load a motor? A couple ideas I had include: ...
• 31
1 vote
103 views

### How do you mount a polystyrene foam wheel to a motor?

I have a wheel I CNC milled out of foam and I need to mount a motor to it. I designed and printed a part that would attach the motor to the foam, but I anticipated that the wheels would be wood back ...
2k views

### What would happen if we tried to run a motor in space when it is not attached to anything to provide support to it?

I know that when a motor runs it generates torque and that torque can be used to do useful work. On the other hand, the motor needs strong support that absorbs the reaction torque. In our case let us ...
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### What is this small rotating part from a cell phone?

What is this tiny rotating piece of hardware that I found inside my Samsung GE1202? It has E9C written in blue on it.
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### How do you calculate the best gear reduction for max speed?

I know that a gear reduction would decrease the RPM if the motor ran at constant speed, but in reality its speed is a function of the load. I first tried turning a wheel with a direct drive system, ...
629 views

### Upgrading to a brushless motor

I have a mini-lathe with a 500W 3/4 HP variable speed motor, that is run by a controller at two different gearings. However, even at the LOW gearing I find the torque to be a little inadequate. Is it ...
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### What affects an internal-combustion engine's efficiency?

For a gasoline internal-combustion engine, used in accordance with the manufacturer's instructions (specified quality oil, fuel, etc. used), what changes the efficiency of the motor? For example at ...
• 366
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### How to calculate if a motor is strong enough

I am building a machine for a project that should slowly tip a screen forward about 95 degrees, hold for a couple of seconds, and then slowly return to vertical. The design I am working on uses two ...
• 41
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### Avoid snapping an electric cable from too much rotation

I recently built the basic construction for a crane out of lightweight material. Basically the head of the crane contains an electric servo motor which spins the head of the crane by pushing itself ...
• 387
1 vote
247 views

### How can I choose a motor for my project? [closed]

I'm working in a project that consists of something similar to a motorized skate. I know how to do it, but I don't know what motor to use. I need that the skate to be able to move 90 Kg to 20 Kph (12 ...
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1 vote
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### Is there a universally accepted way to refer to choosing a more powerful motor for an application?

One antonym word I can think of is "derating". If I say "derate motor for pump X", it can mean "select a motor with lower power output, since the pump doesn't need a more powerful motor". But what ...
• 113
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### Air compressor that doubles as a pneumatic motor?

I am working on a compressed air energy storage system. The size and weight of the system are heavily constrained; nothing should (ideally) exceed a few pounds. For this reason, I would like to store ...
• 93
28k views

### What is Starting Torque?

I'm having a hard time finding an answer from the internet. What does starting torque mean?
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### Validation of transfer function

I have developed a second order transfer function model for a permanent magnet dc motor in terms of speed and voltage. I had performed open loop no load experiments on the dc motor and derived the ...
3k views

### Why does public transport uses compressed air to open doors instead of electromotors?

System with compressed air seems more expensive and harder to build and integrate neither using simple electromagnetic drives to open public transport doors.
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### How to calculate the steps needed for a motor to rotate a circular object in a pulley configuration?

I have a stepper motor with 200 steps per revolution and a pulleys configuration as following: 3 pulleys with 100 mm diameter each on 1184 mm PCD and are equally spaced (120 degrees) from each other. ...
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### Power and motor current

This is a follow up question to my question here about torque and stepper motors. There Olin explains: Note also that torque isn't the only criterion for a motor. Power is another important one. ...
• 559
85k views

### Understanding required torque for a motor lifting a weight

This is a continuation of me trying to understand torque and stepper motors in my other question. I'm trying to understand the torque a motor would be required to generate to lift a small weight, and ...
• 559
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### Effective ways to drive a single shaft with multiple motors?

To head off the "why not use a bigger motor" question, I'm a high school mentor for an FTC (First Tech Challenge) robotics team, with a bit of a soft mechanical / hardware background. They're ...
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